Galectin-4, a tandem repeat member of the β-galactoside-binding proteins, possesses two carbohydraterecognition domains （CRD） in a single peptide chain. This lectin is mostly expressed in epithelial cells of the in...Galectin-4, a tandem repeat member of the β-galactoside-binding proteins, possesses two carbohydraterecognition domains （CRD） in a single peptide chain. This lectin is mostly expressed in epithelial cells of the intestinal tract and secreted to the extracellular. The two domains have 40% similarity in amino acid sequence, but distinctly binding to various ligands. Just because the two domains bind to different ligands simultaneously, galectin-4 can be a crosslinker and crucial regulator in a large number of biological processes. Recent evidence shows that galectin-4 plays an important role in lipid raft stabilization, protein apical trafficking, cell adhesion, wound healing, intestinal inflammation, tumor progression, etc. This article reviews the physiological and pathological features of galectin-4 and its important role in such processes.展开更多
Human T cell leukemia virus type 1(HTLV-1),an etio-logical factor that causes adult T cell leukemia and lym-phoma(ATL),infects over 20 million people worldwide.About 1 million of HTLV-1-infected patients develop ATL,a...Human T cell leukemia virus type 1(HTLV-1),an etio-logical factor that causes adult T cell leukemia and lym-phoma(ATL),infects over 20 million people worldwide.About 1 million of HTLV-1-infected patients develop ATL,a highly aggressive non-Hodgkin's lymphoma without an effective therapy.The pX region of the HTLV-1 viral genome encodes an oncogenic protein,Tax,which plays a central role in transforming CD4+ T lymphocytes by deregulating oncogenic signaling pathways and promoting cell cycle progression.Expression of Tax following viral entry is critical for promoting survival and proliferation of human T cells and is required for initiation of oncogenesis.Tax exhibits diverse functions in host cells,and this oncoprotein primarily targets IκB kinase complex in the cytoplasm,resulting in persistent activation of NF-κB and upregulation of its responsive gene expressions that are crucial for T cell survival and cell cycle progression.We here review recent advances for the pathological roles of Tax in modulating IκB kinase activity.We also discuss our recent observation that Tax connects the IκB kinase complex to autophagy pathways.Understanding Tax-mediated pathogenesis will provide insights into development of new therapeutics in controlling HTLV-1-associated diseases.展开更多
The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human P...The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human PrPc, mouse PrPc or mouse PrP^C carrying the 3F4 epitope, this study explored the influence of the PrP^C primary sequence on endoproteolytic cleavage and one putative PrPc function, MAP kinase signal transduction, in response to exogenous copper with or without a perturbed membrane environment. PrPc primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat- ed kinase 1/2 （ERK1/2） phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrP^C showed increased N1/C1 cleavage in response to copper alone, accompanied by specific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrP^C-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPc harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPc pri- mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence appears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of PrP^C-related signal transduction in response to exogenous stimuli.展开更多
The first appearance of lipid rafts, or lipid rafts-like structure, was occasionally observed by cryo-electronic microscopy in 1980s as cavity, such as caveolae. However, the fully understanding of lipid raft was attr...The first appearance of lipid rafts, or lipid rafts-like structure, was occasionally observed by cryo-electronic microscopy in 1980s as cavity, such as caveolae. However, the fully understanding of lipid raft was attributed by the studies of T cell activation, virus entry/budding, and other membrane events. During the interaction of T cell and antigen presenting cell, a highly organized structure is formed at the interface of the two cells, where cholesterol and sphingolipids are enriched, and form a liquid ordered phase that facilitates the signaling proteins on and off. Lipid rafts are also involved in virus entry and assembly. In this review, we will discuss cholesterolsphingolipid floating microdomain, the lipid raft as a unique compartment of the plasma membrane, with biological functions that ensure correct intracellular traffic of proteins and lipids, such as protein-protein interactions by concentrating certain proteins in these microdomains, while excluding others. We also discuss the disruption of lipid rafts is related to different diseases and aging, and we especially exploit the lipid rafts as pharmaceutical targets for anti-virus and anti-inflammation, particularly a new approach to control HIV infection for AIDS prevention and protection by inhibition or disruption of lipid rafts. Cellular ＆ Molecular Immunology.展开更多
文摘Galectin-4, a tandem repeat member of the β-galactoside-binding proteins, possesses two carbohydraterecognition domains （CRD） in a single peptide chain. This lectin is mostly expressed in epithelial cells of the intestinal tract and secreted to the extracellular. The two domains have 40% similarity in amino acid sequence, but distinctly binding to various ligands. Just because the two domains bind to different ligands simultaneously, galectin-4 can be a crosslinker and crucial regulator in a large number of biological processes. Recent evidence shows that galectin-4 plays an important role in lipid raft stabilization, protein apical trafficking, cell adhesion, wound healing, intestinal inflammation, tumor progression, etc. This article reviews the physiological and pathological features of galectin-4 and its important role in such processes.
基金supported by a grant from National Institute of Health to H.Cheng.
文摘Human T cell leukemia virus type 1(HTLV-1),an etio-logical factor that causes adult T cell leukemia and lym-phoma(ATL),infects over 20 million people worldwide.About 1 million of HTLV-1-infected patients develop ATL,a highly aggressive non-Hodgkin's lymphoma without an effective therapy.The pX region of the HTLV-1 viral genome encodes an oncogenic protein,Tax,which plays a central role in transforming CD4+ T lymphocytes by deregulating oncogenic signaling pathways and promoting cell cycle progression.Expression of Tax following viral entry is critical for promoting survival and proliferation of human T cells and is required for initiation of oncogenesis.Tax exhibits diverse functions in host cells,and this oncoprotein primarily targets IκB kinase complex in the cytoplasm,resulting in persistent activation of NF-κB and upregulation of its responsive gene expressions that are crucial for T cell survival and cell cycle progression.We here review recent advances for the pathological roles of Tax in modulating IκB kinase activity.We also discuss our recent observation that Tax connects the IκB kinase complex to autophagy pathways.Understanding Tax-mediated pathogenesis will provide insights into development of new therapeutics in controlling HTLV-1-associated diseases.
文摘The copper-binding, membrane-anchored, cellular prion protein （PrP~） has two constitutive cleavage sites producing distinct N- and C-terminal fragments （N1/C1 and N2/C2）. Using RK13 cells expressing either human PrPc, mouse PrPc or mouse PrP^C carrying the 3F4 epitope, this study explored the influence of the PrP^C primary sequence on endoproteolytic cleavage and one putative PrPc function, MAP kinase signal transduction, in response to exogenous copper with or without a perturbed membrane environment. PrPc primary sequence, especially that around the N1/C1 cleavage site, appeared to influence basal levels of proteolysis at this location and extracellular signal-regulat- ed kinase 1/2 （ERK1/2） phosphorylation, with increased processing demonstrating an inverse relationship with basal ERK1/2 activation. Human PrP^C showed increased N1/C1 cleavage in response to copper alone, accompanied by specific p38 and JNK/SAPK phosphorylation. Combined exposure to copper plus the cholesterol-sequestering antibiotic filipin resulted in a mouse PrP^C-specific substantial increase in signal protein phosphorylation, accompanied by an increase in N1/C1 cleavage. Mouse PrPc harboring the human N1/C1 cleavage site assumed more human-like profiles basally and in response to copper and altered membrane environments. Our results demonstrate that the PrPc pri- mary sequence around the N1/C1 cleavage site influences endoproteolytic processing at this location, which appears linked to MAP kinase signal transduction both basally and in response to copper. Further, the primary sequence appears to confer a mutual dependence of N1/C1 cleavage and membrane integrity on the fidelity of PrP^C-related signal transduction in response to exogenous stimuli.
文摘The first appearance of lipid rafts, or lipid rafts-like structure, was occasionally observed by cryo-electronic microscopy in 1980s as cavity, such as caveolae. However, the fully understanding of lipid raft was attributed by the studies of T cell activation, virus entry/budding, and other membrane events. During the interaction of T cell and antigen presenting cell, a highly organized structure is formed at the interface of the two cells, where cholesterol and sphingolipids are enriched, and form a liquid ordered phase that facilitates the signaling proteins on and off. Lipid rafts are also involved in virus entry and assembly. In this review, we will discuss cholesterolsphingolipid floating microdomain, the lipid raft as a unique compartment of the plasma membrane, with biological functions that ensure correct intracellular traffic of proteins and lipids, such as protein-protein interactions by concentrating certain proteins in these microdomains, while excluding others. We also discuss the disruption of lipid rafts is related to different diseases and aging, and we especially exploit the lipid rafts as pharmaceutical targets for anti-virus and anti-inflammation, particularly a new approach to control HIV infection for AIDS prevention and protection by inhibition or disruption of lipid rafts. Cellular ＆ Molecular Immunology.
